Antidepressant Drugs and COVID-19: A Review of Basic and Clinical Evidence.

The COVID-19 pandemic has encouraged the repurposing of existing drugs as a shorter development strategy in order to support clinicians with this difficult therapeutic dilemma. There is evidence to support the theory that some antidepressants can reduce concentrations of different cytokines in humans and animals and, recently, the antiviral activity of some antidepressants against SARS-CoV-2 has been reported. The aims of this narrative review are to evaluate the possible role of antidepressants in the treatment of COVID-19 infection and the possible benefits and risks of patients taking antidepressants for mental disorders and COVID-19 infection. A review was performed to analyse the current literature to identify the role of antidepressant medication in the treatment of COVID-19 patients. The electronic search was completed in MEDLINE and MedRxiv/BioRxiv for published literature and in ClinicalTrials.gov for ongoing clinical trials. The results show some evidence from preclinical data and observational studies about the possible efficacy of some specific antidepressants for treating COVID-19 infection. In addition, two published phase II studies testing fluvoxamine showed positive results for clinical deterioration and hospitalization rate versus a placebo. Seven ongoing clinical trials testing fluvoxamine, fluoxetine, and tramadol (as per its anti-inflammatory and antidepressant effect) are still in the early phases. Although the available evidence is limited, the sum of the antiviral and anti-inflammatory preclinical studies and the results from several observational studies and two phase II clinical trials provide the basis for ongoing clinical trials evaluating the possible use of antidepressants for COVID-19 infection in humans. Further investigations will be needed to support the possible use of antidepressants for this application.

Exclusion of NFAT5 from mitotic chromatin resets its nucleo-cytoplasmic distribution in interphase.

BACKGROUND: The transcription factor NFAT5 is a major inducer of osmoprotective genes and is required to maintain the proliferative capacity of cells exposed to hypertonic stress. In response to hypertonicity, NFAT5 translocates to the nucleus, binds to regulatory regions of osmoprotective genes and activates their transcription. Besides stimulus-specific regulatory mechanisms, the activity of transcription factors in cycling cells is also regulated by the passage through mitosis, when most transcriptional processes are downregulated. It was not known whether mitosis could be a point of control for NFAT5. METHODOLOGY/PRINCIPAL FINDINGS: Using confocal microscopy we observed that NFAT5 was excluded from chromatin during mitosis in both isotonic and hypertonic conditions. Analysis of NFAT5 deletions showed that exclusion was mediated by the carboxy-terminal domain (CTD). NFAT5 mutants lacking this domain showed constitutive binding to mitotic chromatin independent of tonicity, which caused them to localize in the nucleus and remain bound to chromatin in the subsequent interphase without hypertonic stimulation. We analyzed the contribution of the CTD, DNA binding, and nuclear import and export signals to the subcellular localization of this factor. Our results indicated that cytoplasmic localization of NFAT5 in isotonic conditions required both the exclusion from mitotic DNA and active nuclear export in interphase. Finally, we identified several regions within the CTD of NFAT5, some of them overlapping with transactivation domains, which were separately capable of causing its exclusion from mitotic chromatin. CONCLUSIONS/SIGNIFICANCE: Our results reveal a multipart mechanism regulating the subcellular localization of NFAT5. The transactivating module of NFAT5 switches its function from an stimulus-specific activator of transcription in interphase to an stimulus-independent repressor of binding to DNA in mitosis. This mechanism, together with export signals acting in interphase, resets the cytoplasmic localization of NFAT5 and prevents its nuclear accumulation and association with DNA in the absence of hypertonic stress.

Regulation of the hypertonic stress response and other cellular functions by the Rel-like transcription factor NFAT5.

Stress, be it from environmental factors or intrinsic to the cell as result of growth and metabolism, can be harmful to cells. Mammalian cells have developed numerous mechanisms to respond to diverse forms of stress. These mechanisms combine signaling cascades and activation of gene expression programs to orchestrate an adaptive response that will allow the cell to survive and resume its normal functioning. In this review we will focus on the transcription factor NFAT5, a fundamental regulator of the response to osmotic stress in mammalian cells. Identified in 1999, NFAT5 is the latest addition to the Rel family, which comprises the NF-kappaB and NFATc proteins. Though in some of its structural and functional features NFAT5 is a hybrid between these two major groups of Rel proteins, it has unique characteristics that make it stand on its own as a third type of Rel transcription factor. Since its discovery, NFAT5 has been studied mostly in the context of the hypertonicity stress response. The advent of mouse models deficient in NFAT5 and other recent advances have confirmed a fundamental osmoprotective role for this factor in mammals, but also revealed features that suggest it may have a wider range of functions.